Interrupted Rocksnail

Description: Has moderately thick shell (approaching 20 mm [3/4 in.] long), elongately globose in outline, generally with no more than three whorls present. Small folds (incised striae) cover body whorl from suture to base, but are weaker basally. Dorsal edge of each suture accented by several heavy plicae that are irregularly formed and varied in size. Plicae do not extend far onto body whorl, and may be nearly absent in some individuals. Folds surrounding body whorl are nearly straight basally, but are more undulating as they approach suture and cross plicae. Periostracum light brown to burnt orange, but folds may be darker, giving shell a mottled appearance. Juveniles tend to be more lightly colored (nearly orange). Body weakly convex and shell spire elevated considerably with increasing size, an unusual character in genus. Sutures deeply impressed, but weak shoulders diminish overall appearance. Columella dark purple to nearly white, darkening basally, and folded to cover umbilicus completely. Juveniles have tightly coiled whorls, display strong folds and plicae, distinguishing L. formani juveniles from other Leptoxis species. Operculum red to maroon, with coarse growth lines widely spaced across surface. (Modified from Lea 1868, Goodrich 1922)

Distribution: Endemic to Coosa River system and historically occurred from its headwaters in northwestern Georgia: Conasauga, Coosawattee, and Etowah River systems, downstream to Elmore County, Alabama. Historically present in lower reaches of Terrapin Creek, Cherokee County. Species extant in a 12 kilometers (7.4 miles) reach of Oostanaula River, Gordon and Floyd Counties, Georgia.

Habitat: In Oostanaula River, occurs in shoal and shallow run habitats. Shows preference for currents between 20 and 40 centimeters per second (8-15 inches per second) and most abundant in areas less than 40 centimeters (15 inches) deep (Johnson and Evans 2000). Preferred substratum a mixture of smooth gravel, cobble, and boulders, free of fine sediments (Johnson and Evans 2000). Does not occur on bedrock or aquatic vegetation.

Life History and Ecology: Females lay multiple clutches of 11 to 24 eggs from March until mid-May and eggs hatch in seven to 10 days at 20°C (68°F) (P. D. Johnson, unpubl. data). Egg clutches laid in a concentric circular pattern, near air-water interface or in well-oxygenated riffle habitats. Do not reproduce until its second year and may live up to five years (P. D. Johnson, unpubl. data). Grazes on silt-free gravel, cobble, and boulders.

Basis for Status Classification: Vulnerable to extinction due to highly restricted distribution, small population size, and specific habitat requirements. May be most imperiled Leptoxis in Mobile Basin. Considered extinct until rediscovery in 1997. Listed as endangered in Alabama (Stein 1976). Eliminated from more than 95 percent of historical distribution. Now a candidate for federal protection by the U.S. Fish and Wildlife Service.